gbg

On my MTB with a 44/32/22 crankset and 34-11 cassette and a nice tail wind I could get
use of my highest gears for a few minutes every few rides if I wanted (see red numbers, no it is not my average speed). No hills up here so this is on the flats.

REVOLUTIONS PER MINUTE
SP CRxFW GI | 85 90 95 100 105 110 115
15> 44x20 57.20 MPH: 14.46 15.32 16.17 17.02 17.87 18.72 19.57
16> 32x13 64.00 MPH: 16.18 17.14 18.09 19.04 19.99 20.94 21.90
17> 44x17 67.29 MPH: 17.02 18.02 19.02 20.02 21.02 22.02 23.02
18> 32x11 75.64 MPH: 19.13 20.25 21.38 22.50 23.63 24.75 25.88
19> 44x15 76.27 MPH: 19.29 20.42 21.55 22.69 23.82 24.96 26.09
20> 44x13 88.00 MPH: 22.25 23.56 24.87 26.18 27.49 28.80 30.11
21> 44x11 104.00 MPH: 26.30 27.85 29.39 30.94 32.49 34.03 35.58

Since I haven't had a road bike for a long time (been riding MTB'S) I felt the need for speed and I recently bought a road bike with:

53/39 crank and a 27/12 cassette (have a 12/23 and 12/25 but just tried the 12/27 first).
Today I saw there were winds 35km/h (21mph) gusting to 50 km/h (30mph) so conditions looked ripe for a high speed run on the return journey of my 25 mile ride (riding out was no fun, since it was 10C/50F as well). Unfortunately gusty was an understatement and on the way home they were switching from 90 degrees from my right to almost behind me and back again. So as I was hitting the mid 30's and with traffic to my left (and a s***y section of road) I backed off, this is when I realized I was only in my 53/14.
Since there are no hills around WHEN THE H*** WILL I USE 13 and 12!!

| REVOLUTIONS PER MINUTE
SP CRxFW GI | 85 90 95 100 105 110 115
-----------------------------------------------------------------------------
10> 53x16 91.43 MPH: 23.12 24.48 25.84 27.20 28.56 29.92 31.28
11> 53x15 97.52 MPH: 24.66 26.11 27.56 29.01 30.46 31.91 33.36
12> 53x14 104.49 MPH: 26.42 27.98 29.53 31.08 32.64 34.19 35.75
13> 53x13 112.52 MPH: 28.45 30.13 31.80 33.48 35.15 36.82 38.50
14> 53x12 121.90 MPH: 30.83 32.64 34.45 36.27 38.08 39.89 41.70


Even though there are only a few MPH difference I wonder if this makes more sense?
At least there will be a chance of getting use of 13 and 12.

SP CRxFW GI | 85 90 95 100 105 110 115
10> 50x16 86.25 MPH: 21.81 23.09 24.38 25.66 26.94 28.23 29.51
11> 50x15 92.00 MPH: 23.26 24.63 26.00 27.37 28.74 30.11 31.48
12> 50x14 98.57 MPH: 24.93 26.39 27.86 29.32 30.79 32.26 33.72
13> 50x13 106.15 MPH: 26.84 28.42 30.00 31.58 33.16 34.74 36.32
14> 50x12 115.00 MPH: 29.08 30.79 32.50 34.21 35.92 37.63 39.34

Sawtooth

I like your data driven approach. I personally am facing the same question (for climbing purposes) but tend to analyze the issue using gear inches instead of MPH. THis allows me (with experience in the respective gear inches) to control for things such as wind conditions, hills, etc.

In the end, I am leaning away from the compact because my sweet spot for easy cruising (73 gear inches) is more available with the standard. I still may end up picking up a compact for my more mountain-intensive rides (more than 30 miles of steep climbing).

On a side note, I am successfully running a 12-32 with a 48/38 on my cyclocross bike and there is almost nothing I can't climb with that. It also makes a great commuter set up. I have also done a couple of road centuries on that gearing and loved it.

On the road I only use the 53/12 for reaching speeds well in excess of 35 mph (that usually means hills). I hit 52 mph on my saturday ride!!!!!

gbg

I looked at gear inches but MPH just seems more understandable to me.
Since there are no hills around here, I should probably look at my "sweet spot" for riding as well.
With my MTB and 22/34 I don't think there anything it can't climb (that's less than 1:1 crank rotation/wheel rotation) I never thought I would use it but I did, and in all places IOWA (it ain't flat, especially along the Mississippi).

Since I have only been out on the road bike 3 times I'll probably see how it goes for awhile with the standard.

Hunt-man

I need a compact because I live in Portland, OR on top of a 750' hill. So every ride ends with a big climb. If all you have is flat ground why get a compact? I just do the compact to save my knees. Lots of my ridding buddies don't ride a compact, even with all the hills we have and ride.

DannoXYZ 

If the low gears are sufficient, you can just install a 50t chainring on your existing crank.

roy5000x2

If you're wondering when you're going to use the 12 and 13 tooth cogs, that would be on a downhill. If you don't think you're ever going to use them, it'd be cheaper to buy a cassette that starts at 14t or put on a 50t chainring in front than to buy a whole new crank.

gbg

I'm not sure if I can get a 50 tooth for a Dura Ace crankset, I will have to look around. The only thing I'm concerned about is I heard compacts aren't that great shifting, and I really like my front shifting now. And adding just a 50 might not be that great for shifting as well. Since it is only the start of the season maybe I'll suck it up and wait till I get in better shape in the next few weeks.
Thanks.

bjupton

I think the concern there is that you are talking a 16 tooth difference (50-34) vs the 14 difference (53-39).

I think this was more of a concern when CDs were realtively newer, but much less so now.

AEO

if you get shimano chainrings, there will be no issue with shifting performance as long as you adjust your derailers properly.

yogi13

Maybe some day you'll develop massive guads and be able to dial it up to 400 watts when you drope the hamer, and you'll need the 12T & 13T...or maybe you'll use them on the rare occasion when you've got a 25+ mph wind directly at your back...or maybe they just sit there until you need them on a hilly charity ride in another state. Either way, no need for a compact.

FWIW, I get into my 12T or 13T on nearly every ride when I hit a section of road that has a false flat downhill and the wind nearly always blows at my back. It's quite a thrill to briefly get up to the mid-30's, even though that's cheating a bit.